Pressure-relief device



April l951 o. FITZ sMoNs 2,548,298

PRESSURE RELIEF DEVICE Filed July 24, 1946 x /L/ //,O

. lNVENTOR days/v ;772 5/M0/V5.

ATTORNEY Patented Apr. 10, 1951 UNITED- STATES OF-F'I CEE 2548,298 iPRESSURE-.RELIEF DEVICE :QgdemFitz Simons; WebsterGroveMo., :assig orogMonsanto -Chemical Company, St. Louis,Mo.,

acorporation ofJD'elaware v "This invention relates to mptu-re discs;for use in reactionzkettles or in other places where su'd- ;den surges:of pressure mustbe :quickly 'vented More particularly, the inventionrelates to inexpensive rupture discs and meth'ods for' regulating'thes'trength of the .discs.

Rupture discs or explosion discs are used `in teaction vessels torelieve 'sudden apressuresurges which might :cause .serious :damage if;they we're not quickly dissipated. various materials have been used formaking these discs such as metals including iron, steel, lead, silver,platinum and gold. The type of material used depends partly on thereactants in the reaction chamber. For example, if the pressure isexerted by an inert gas such as m'trogen, the material of the rupturedisc is unimportant, but if it is steam or a corrosive liquid or gas,great care must be taken in selecting the material of the rupture discto prevent contamination of the material in the re-.

action chamber.

Attempts have been made in the past to use glass for rupture discsbecause of its relatively great resistance to most chemicals but nomethod has been found which will allow reasonably accurate control ofthe rupture point of glass discs. Thus, when glass discs were used, therupture point varied between and 100 pounds per square inch forapparently similar discs. i

It is an object of this invention to provide glass rupture discs. Afurther object of this invention is to provide glass rupture discs whichwill break within a relatively narrow pressure range.

These and other objects are attained by using for a rupture disc, glassat least one surface of which has been roughened by sand blasting,grinding or etching. By careful selection of the thickness of the glassto be used in the discs and by controlling the nature of the roughenedsurface relatively accurate control of the bursting point is attained.

This invention is more clearly disclosed by reference to the drawings inwhich Fig. 1 is a top plan View of a glass rupture disc set within afiange.

Fig. 2 is an enlarged cross-section taken along lines 2-2 in Fig. 1looking in the direction of the arrows.

Fig. 3 is an enlarged cross-section of the preferred type ofglassrupture disc.

Fig. 4 is an enlarged cross-section of an alternate type of glassrupture disc. p

In Figs. 1 and 2 there is shown a method for assembling glass rupturediscs 'in an explosion vent on a suitable reaction vessel, not shown.

-1-.Claim. (01.::220-489) !I'he glass rupturedisc:l his sealedavithin aflange I of a wentpipegl, using -igaskets, 44, to seal the glass ;to theflanges and -to -prevent breaking .the glass when the fianges aretightened. The smoothsurfaces i l 6 "at :the i edges of -the upper andlower ;faces :of .the discs -serve to :give -a leakproof seal withthezgaskets.

The glass rupture disc :H :has a roughened sur face !5. This surface maybesobtained by sand blasting, -grinding, nor by etching or by otherknown means for producing a fine pebbly or grainy surface on glass.Preferably, the roughened surface covers only that portion of the glasswhich is subject to rupture from pressure surges in the reactor and maybe carried on only the surface of the glass rupture disc facing the lowpressure side of the system. However, as shown in Fig. 4, both faces ofthe rupture disc may carry roughened portions, if desired, to givesomewhat better control of the critical rupturing point. The smoothpolished portions [6 give a good seal as already pointed out.

In the embodiment shown in Fig. 3, one surface of disc ll is sandblasted so that portion !5 is concave, providing a point IT 'in aboutthe center of the disc which is thinner than the original glass by ameasured amount. For purposes of illustration, the concave portion isgreatly exaggerated in Fig. 3. This concave surface is a means forincreasing the control over the pressure at which the disc will ruptureby changing the thickness of the original glass to meet the specificpressure requirements and then As typicalof the rupture characteristicsof the lass 'explosion discs of this invention, a number of circularpieces ofplate glass :7% inch thick and 6 inches in 'diameter were sandblasted on one side. The sand blasted portion covered a circular area inthe center of the disc approximately 4 inches in diameter. The sandblasting had' been carried out to producea concave surface the centralpoint of which was about .015 inch thinner than the original plate.These discs Were used in the pressure relief vent of a reaction kettlein which the pressure was provided by hydrogen chloride. The thicknessof the glass of the sand blasted area was chosen to provide a burstingpoint of 15 pounds per square inch. Three of the plates were brokenunder controlled conditions and were found to burst at approximately 14,15 and 17 pounds per square inch. Thereafter, imilar discs were used inregular production units and no failures at too low or too high apressure were observed.

The thiekness of the glass may be varied to obtain different burstingpoints. For example, by reducing the thickness to %3 inch the bursting.point was reduced to about 12 p. s. i. 'For higher bursting pressure,thickness up to inch may be used.

The glass rupture plates of this invention have i the advantage thatthey are relatively cheap and' u it is easy to regulate their burstingpoint. Furthermore, *they are not attacked by Corrosive liquids andgases and therefore will not contaminate the reaction if pieces of theplates fell into the reaction vessel. r r

It is obvious that many Variations can be made in the products andprocesses of this invention without deviating from its spirit and scopeas set forth in the appended claim.

What is claimed is: v

An explosion protector for reaction vessels,

4 comprising flange and a glass rupture disc sealed in gas-tightrelationship between said fianges, said disc comprising plate glass ofwhich at least one fiat surface carries a central concave finely 5 rouhened portion.

OGDEN FITZ SIMONS.

t file of this patent:

UNITED STATES PATENTS Number Name Date 540, 119 Burlingame June 4, 189515' I &333,694 Parker Oct. 16, 1906 1,240,398 Wood Sept. 18, 19171,429,296 Obert Sept. 19, 1922 1,556,796 Minter Oct 13, 1925 `1565369Straw Dec. 15, 1925 20 2,143,796 Phillips Jan. 10, 1939 2,178,178McKeever Oct. 31, 1939 2,261,035 Miller Oct. 28, 1941 '2,398308 HendrixApr. 16, 1946 OTHER REFERENCES Sand Blasting and How It is Done," onpage 26 of Pottery and Glassware Reporter, dated December 29, 1887. (Acopy of this article may be found in Div. 67, class 11, subclass 39.)

